Hi

Recently I took some photographs "through" a reflection. I focused on the plane of glass, not the virtual distance of the subjects within the reflection (I use a rangefinder so I don't have direct DOF feedback). Some were totally out of focus. Some turned out because I stopped down.

From prior experience with an SLR I seem to recall that I needed to focus on the virtual distance to the subject i.e. "past" the plane of the mirror. Is that true or am I hallucinating?

Thanks

-- Asher (schachter@a1.tch.harvard.edu), November 18, 1999

Answers

If you were to focus on a piece of lint on the mirror, then the plane of the mirror should be the plane of focus. In your case, you need to focus on the actual subject as the subject appears on the reflection, beyond the plane of the mirror.

-- Tony Rowlett (rowlett@alaska.net), November 18, 1999.

The mirror creates an image that is behind the mirror. If you want that image to be in focus, you should focus on it.

-- Alan Gibson (Alan.Gibson@technologist.com), November 18, 1999.

In other words, your camera to subject distance is the sum of the distance of the camera to the mirror PLUS the mirror to the object that it is reflecting.

-- chuck k (kleesattel@wetv.com), November 19, 1999.

When you take a photo of a reflecting sphere (like the things on the christmas tree), however, focus on the sphere.

-- Thomas Wollstein (thomas_wollstein@web.de), November 22, 1999.

Asher-

Sorry to be coming in on this so late, but I feel I had to include my 2 cents.

It has always been a mistery why someone feels that they have to focus on something all the time. In the situation of the mirror and the subject in the mirror, I assume that you wanted both the mirror and the subject in focus. The best way to do this is not to focus on the mirror or the subject, but somewhere inbetween. The best way to determine the point of focus is to determine the distance from the camera to the mirror and then the distance from the camera to the subject. Some cameras give you a footage reference at that focus. Then find an F stop that has a DOF which will include the entire distance. Again, on some cameras you can match F stop numbers with feet markings on the lens. Put the first F stop on the foot mark for the closest point. The the same F stop on the other side of the scale on the foot mark for the furtherest point. Alow a little more on each side of the scale for error. If you do not have the time or equipment to measure, stop down as much as you can hand hold the camera and focus between the two points.

I have done this with reat success.

Greg

-- Greg Bates (avalon@bendnet.com), December 06, 1999.